Impeachment? Why?

Jon Chait seems to think that if the GOP wins control of the House, it will impeach Obama.  Jonah Goldberg offers him a $500 bet that it won't happen.  I tend to agree with Goldberg -- if Obama's approval ratings continue to slide, he's more valuable to the GOP in office leading up to 2012 than battling an impeachment trial where he becomes a victim.  I think Chait's trying to raise the alarm because he's trying to help wake up Democrats, and on what I'll henceforth call the "Dumb and Dumber" theory -- there's a chance, even if it's one in a million, and then he could waive around his prediction (or his computer) proclaiming his own genius.

Meanwhile, two questions.  First, does this mean Chait thinks Obama's perjured himself recently?  Second, if this did happen, would this mean that the GOP had impeached America's first two black Presidents (Clinton and Obama)?